FedEx MD-10 Freighter; DC-10 or MD-11?

We are visiting the 1997 Boeing MD-10 program which involved retrofitting 1970’s era DC-10 flight decks to the standard of the modern MD-11 avionics architecture. The installation of a 2 flight crew members flight deck in place of the traditional DC-10’s 3 flight crew members would cement commonality between both types. For FedEx Express which operates both aircraft types as core to its globally integrated logistics operation, this program provided opportunity to facilitate inter-operation between both types, thus allowing entire wide body/long range fleet rationalization into a single aircraft type. For a large scale highly integrated global logistic operation, such standardization also signified propagating tangible cost savings deeper across the entire logistics architecture.

FedEx Express acquired its first Douglas Aircraft Company’s DC-10-10 in 1980. Type certificate for the DC-10-10 passenger version was first issued July 29,1971 with DC-10-30 receiving type certificate November 21st 1972. The MD-11 type certificate arrived almost twenty years later on November 8th 1990. The MD-11 was proposed as a logical replacement for the obsolescent but still robust DC-10 (of which 446 aircraft had been built between 1970 and 1989). Both MD-11 and DC-10 showed the same basic nontraditional design involving two high bypass ratio turbofans engine attached to under wing pylons supplemented by a third engine mounted at the vertical tail’s base on top the fuselage. This approach provisioned the aircraft for a wider variety of high range/payload requirements in niche market .The seemingly identical appearance and design principle between MD-11 and DC-10, indicated that manufacturer McDonnell Douglas (who took over from Douglas) had retained the basic features that were already proven on the DC-10 program. This was a great selling point for operators worried that a completely new airplane design would not fit with established logistics processes. However the twenty years age difference between both types also meant that a new regime of technological improvements were available on the MD-11, particularly the innovative state of the art cockpit that was now operated by 2 pilots instead of 3 on DC-10s. For FedEx, this also meant that the highly integrated logistic operation at its global hubs which had been designed to take advantage of the DC-10 Freighter unique configuration could seamlessly integrate with the MD-11 near identical fuselage layout.

The DC10-10

The DC-10-10 passenger version that was certified by the Federal Aviation Administration on July 29th, 1971 provided a typical maximum take-off gross weight of between 440,000 lbs and 455,000 lbs. Operators ordering this model could select from either one of three General Electric high by-pass ratio turbofan engines; the CF6-6D/-6K (chosen by FedEx had 39,300 lbs thrust), CF6-6D1 (40,300 lbs thrust) and CF6-6D1A/-6K2 (40,900 lbs thrust). The Airplane Performance Manual performance chart indicated a range of 2,500 nm (2,877 mile) with the 399 maximum passengers plus baggage (94,745 lbs total payload) on board, cruising between 31,000 and 35,000 ft at a Mach 0.82 speed. The full cargo version offered less than the 2,500 nm (2,877) range when carrying the 119,556 lbs designed maximum payload. The aircraft dimensions were 182 ft 3.1 in (55.55 meters) in overall length and 155 ft 4 in (47.35 meters) wingspan allowing a passenger version’s seating arrangement of 8 abreast (2-4-2) in coach on a 2-class configuration (270 passengers) but a high density configuration that could force 399 passengers aboard sat 10 passengers abreast (3-4-3) as in the Boeing 747. The all-cargo version equipped with the main deck large cargo door in the forward left section could fit 30 pallets (88 in x108 in) or 22 pallets (88 in x 125 in). The lower cargo holds accommodated bulk along with 14 to 26 (DC-10-30) LD3 containers (depending on the amount of bulk cargo).

The DC10-30

The DC10-30 aircraft optimized for intercontinental operations received FAA certification on November 21, 1972. It essentially provided a stretched fuselage version of the DC-10-10. The overall length of the aircraft increased to 181 ft 7.2 in (55.35 meters). An accompanying increase in wingspan to 165 ft 4 in (50.39 meters) meant significant increase in payload and range. The introduction of the more powerful General Electric CF6-50A/-50C family of engine with a thrust of 51,800 lbs (specific to the CF6-50C2 used by FedEx) along with the fuselage stretch contributed to a logical increase in maximum take off weight varying between 565,000 and 572,000 lbs with some airlines ordering airframe that even reached the 590,000 lbs MTOW threshold. The DC-10-30 additional weight was betrayed by the introduction of a third set of wheels to the main landing gear. The freighter version could carry a 152,551 lbs payload at approximately 3,200 nm (3,682 miles), typically 22 (88 in x 125 in) pallets on the main deck and 26 LD3 containers in the lower cargo hold alongside bulk.

The MD11

The MD-11 was FAA certified November 8th 1990 and offered a continuation of the DC-10 family of aircraft with similar fuselage cross-section measurement, a flight crew of 2 instead of 3 on the DC-10 and other technological innovations that improved operating economics by a wide margin. The Honeywell-built fully digital ‘glass’ deck that incorporated traditional aircraft instruments into six 8 in x 8 in CRT electronic displays along with a new automated Aircraft Systems Controllers permitted the elimination of the flight engineer position in the MD-11. Improved aerodynamics performance was also achieved thanks to smaller horizontal stabilizers, installation of winglets, a re-designed tail cone and the Longitudinal Control Augmentation System LCAS computerized roll control system all compounding further drag reduction drag and increased range. The further elongated fuselage led to a even higher Maximum Take Off Weight of 610,000 lbs to 630,500 lbs. New General Electric CF6-80C2D1F or Pratt & Whitney PW4460 and 4462 engines rated for (60,690 lbs thrust, 60,000 lbs and 62,000 lbs respectively) allowed the aircraft to transport 26 pallets (88 in x 125 in) or 26 pallets (96 in x 125 in) on the main deck with additional 6 pallets (96 in x 125 in) or 6 pallets (88 in x 125 in) along with 14 LD3 containers and more bulk cargo bellow deck. The MD-11 payload and range capabilities escalated to 200,000 lbs and 3,500 nm (4,027 miles) respectively. The MD-11 main selling point was its extensive use of computer bringing maintenance and reliability-associated cost savings that could be compounded to the savings realized from the smaller flight crew. Together with the DC-10, the MD-11 would form the backbone of FedEx Express Global freighter fleet in support of which the more limited Airbus wide body A300s, A310s, narrow body Boeing 727-200, along with various smaller aircraft types could be deployed around main hubs.

In 1991, with some 20 DC-10 (8 x 10F and 12 x 30F) already operating (first acquired in 1980), FedEx recognizing that the MD-11 had all the positive attributes of the DC-10 but only with superior capabilities, decided to introduce it in its fleet. By 1997, 23 MD-11 freighters had been acquired and the DC-10 fleet which had solidified to a mix of 41 DC10-10 and DC10-30 Freighters was looking to an increase commonality with the MD-11 fleet.

Hence the MD-10 flight deck modernization program offered by Boeing to retrofit the FedEx 1970’s DC-10’s 3-crew members cockpit to the modern MD-11 two-pilot ‘glass’ cockpit standard. Boeing estimated that with 413 DC-10 built, for airlines operating both MD-11 and DC-10 aircraft, the prospect of a single pilot type certification along with all the cost benefits normally afforded by fleet commonality offered the strongest incentives. The introduction of modern digital computers also offered significant cost savings in on-board equipment weight and ease of maintenance due to reduced number of parts (19 Line Replaceable Units LRU on the MD-10 instead of 50 LRUs on the DC-10) along with computerized fault isolation/determination reporting terminals. The FedEx DC-10 fleet, target of the MD-10 upgrade was scoped by Boeing to number more than 70 aircraft comprising DC10-10 and DC10-30 variants.

(Picture of a FedEx Express MD-11F also on approach)

The MD10 retrofit program.

Critical to the MD-10 upgrade are both the Advanced Common Flight Deck installation and a passenger-to-freighter conversion component as most DC-10 freighters are sourced from the passengers aircraft pool.

I. The MD11 and the Honeywell Advanced Common Flight deck (ACF) architecture

This section allows us to understand in detail operation of the MD-10/MD-11 flight deck.

The MD10 cockpit modernization program relies on the Honeywell Aerospace System built modern avionics suite specifically designed for the MD-11. With the MD11, the system managed to achieve a reduction of flight crew members by one thanks to significantly reduced pilot workload and increased levels of sensor integration on a simplified interface. Motivated by a desire to export the MD11 flight deck success to other aircraft, Honeywell decided to use the MD-11 avionics modular architecture as the foundation of the Advanced Common Flight deck (ACF) which later found its way on the MD-90, Boeing 717, 737, and was even adapted to the Boeing 777. On the MD10, the system is expected to remain identical to the MD-11 as both aircraft must offer a single pilot qualification. Except for updated components such as Liquid Crystal displays being used in replacement of Cathode Ray Tubes and more modern AMD 29xxx Pegasus family of processor chipset. The ‘Architecture’ approach is preferred as it gives the buyer freedom to select purchase Buyer Furnished Equipment from any vendor it chooses to. This ensures that an operator can maintain a consistent line of interchangeable on board equipment (such as navigation sensors) across an entire fleet no matter what the aircraft types.

The six electronic Display Units

The 2-pilots flight deck operation has been fully automated with an Electronic Instrument System (EIS) suite involving six 8in x 8in main Cathode Ray Tube electronic displays (replaced by LCD screens on the MD-10) with prioritized fail over capability in the event of a failure of one DU. The six electronic Display Units (DU) located on the MD-11 main dashboard are responsible for reducing the pilot workload by concentrating information and operation from several flight instruments at one place. The six displays consist of two sets of Primary Flight Displays (PFD)-and-Navigation Displays (ND) in front of each pilot station supplemented by a centrally mounted Engine and Alert Display (EAD) next to a System Display (SD). Operation of the various Display Units is done via the pilot or co-pilot EIS control panel located on either side of the Glareshield Control Panel (GCP) resting above the dashboard.

The System Display is however an exception as its aircraft system monitoring and troubleshooting function requires it to be operated by its own System Display Control Panel located on the look-down center console between the pilot and co-pilot seats. Through it pilots are allowed to page through ten different on-screen schematics views of the aircraft sub systems. This is a practical way for querying the sophisticated Aircraft Systems Controller (ASC) through which a plethora of aircraft systems interface (Environmental control System (ECS), Hydraulic System Controllers, Electrical Power Control Unit (EPCU), Fuel System Controller (FSC) and Ancillary Fuel System Controller (AFSC), Pneumatic System Controller, Air Conditioning Controllers, Cabin Pressure Controllers, Anti-Ice, Cabin Pressure, Cargo Fire, Galley Buses, etc. ) without having to manually revert to these individual aircraft systems control buttons located on the central overhead control panels. In that sense the ASC is almost single handedly responsible for having eliminating the third flight crew aboard the MD-11.

The Automatic Flight System (AFS) and The Flight Control Computer (FCC)

The MD10 Auto Flight System (AFS) interacts with the Flight Control Computer (FCC) to automate control of the airplane throughout the entire phases of flight. The following essential flight functions apply:

Flight Director (FD)

Full flight regime Automatic Pilot (AP)

Full flight regime Automatic Throttle System (ATS)

Autoland Category IIIb,Stall warning, Altitude alerting, automatic ground spoiler, flap limiter and more…Pilots can interact with and program the Auto Flight System (AFS) using the AFS dedicated Control Panel also located on the Glareshield Control Panel. Selectors and switches allow selection for pitch, roll, thrust control modes

as well as speed and altitude programming for various stages of the flight.

The Flight Control Computer (FCC) redundant Versatile Integrated Avionics (VIA 2000) architecture is designed to preserve flight-critical control and processing capabilities in the event of a serious system failure. The FCC directly governs the servos electronic logic and the operation of flight control surfaces actuators for inboard and outboard ailerons and elevators, upper/lower rudder, spoilers and stabilizers. Aircraft flight attitude is determined throughout the entire regime of the flight envelope by integrated control of various surface actuators, throttle servos, flap actuator, auto slat actuator, trim controls, angle of attack sensors, control wheel sensors, etc.

A complete suite of Redundant Voice communication protocols is provided with ground via VHF, HF and SATCOM. Automated Communications Addressing And reporting System (ACARS) capability is provided for automatically transmitting systems faults to the aircraft base of operation for troubleshooting assistance purpose. It is provided by either one of the VHF radio, SATCOM or HF dedicated Data Link. Pilot operation of the Communications system is via Radios panel located on the cockpit pedestal.

The Audio Management Unit (AMU)

The Audio Management Unitoversees the transmission of voice and aural alerts communications. The voice transmission comprises intercom phone system , pilots, Cockpit Voice Recorder operations using the Audio Control Panel. Aural Alerting transmission are generated by the Central Aural Warning System (CAWS), Traffic Alert Collision Avoidance System (TACAS) and Ground Proximity Warning System (GPWS) that also generate visual alerts on the Engine and Alert Display (EAD)

The Maintenance Systems

The Centralized Fault Display System (CFDS) provides testing and fault isolation incorporating ACARS message, identifies faults along with the Line Replaceable Unit from which they originate and even diagnostic of faulty components on the Aircraft Systems Controllers.

The CFDS is supplemented by On-Board maintenance terminal (OMT) and its embedded database of fault messages for correlation with checks conducted on the flight deck. The OMT also maintains digital format storage for the Aircraft Maintenance Manual (AMM), Fault Isolation Manual (FIM), Maintenance Equipment List (MEL) etc. The Multipurpose Control Display Unit MCDU serves as centralized interface for the system.

II The Passenger-to-Freighter Conversion

In 1997, the MD-10 program involved mainly cargo conversions as the days of the 27 years old DC-10 in passenger service were numbered. Most airlines had already ceased operating them for newer more modern wide body aircraft. Continental Airlines, Northwest Airlines and KLM had been few examples of global operators holding on to their DC-10 into the year 2000 however for most Airbus 330 and Boeing 777 were soon to arrive pushing DC-10s to desert storage. The MD10 program offered an incentive to cargo operators by incorporating a freighter conversion into kit. The freighter conversion which was also offered for passenger-only MD 11 consisted of installation of main deck forward cargo door, a rigid cargo barrier RCB restraint system (replacing the crash net and smoke barrier) protecting aircraft structure and the cockpit from the impact of shifting cargo during excessive aircraft motion and the structural reinforcements which allowed the aircraft to incorporate yet another noticeable increase in maximum gross weight. Altogether the aircraft would undergo a heavy maintenance check and receive proper care for structural fatigue issues. We determined that a significant proportion of FedEx DC10-10F received engine changes from CF6-6K to CF6-6D during the 120 days they were undergoing the passenger-to-freighter conversion. Altogether the MD10 upgrade allowed Boeing to shave off approximately 1,000 LB (454 kg) from the aircraft just by installing smaller footprint on-board equipment and elimination of the flight crew. The newly modified airframes introduced the largest increase in gross weight yet for DC-10-10F which achieving a maximum take off weight of 446,000 lb (202,304 kg) with a payload of 143,500 lbs (65,091 kg) for a nonstop range of approximately 2,000 nm ( 2,300 miles ). The DC-10-30F grew their MTOW to 580,000 lb (263,086 kg) with a payload of 180,000 lbs (81,720 kg) for a nonstop range of 3,700 nm (4,255 miles) and MD-11 settling at MTOW of 630,500 lb (286,247 kg) with payload of 201,851 lbs (91,640 kg) with range of 4,000 nm (4,600 miles). On May 9th ,2000 Boeing announced that the FAA had granted the company an amended type certificate and a production certificate of airworthiness for the MD-10 freighter aircraft.

A line of MD-10 Freighters with a pair of Airbus 310 are mixed in.

III The MD10 In Operation

FedEx air currently operates a fleet of approximately 73 DC-10 (-10 and -30 freighters variants) brought up to the MD10 configuration and 60 MD-11 effectively making the MD-10/-11 family the largest aircraft type in its fleet (excluding the little known Cessna 208 Cargomaster ).The 73 MD-10 comprises 18 MD-10-30F equipped with General Electric CF6-50C2 engines and 58 MD-10-10F equipped with General Electric CF6-6D engines.

During FedEx overnight peak global hub operation, it is not uncommon to encounter one third of the entire MD-xx fleet in the air simultaneously. The operational patterns were for the MD-11 to conduct flights as long as Anchorage-Shanghai in 9 hours 18 minutes and Memphis-Sao Paulo in 8 hours 49 minutes. FedEx also operates the type on segments as short as 55 minutes. The MD-10 seems to operate double the amount of flights conducted by the MD-11. However its longest segment is on par with the MD-11 capability; Shannon-Atlanta in 8 hours and 6 minutes. But again MD-10 also conducts very short (37 minutes) flights between Chicago and Indianapolis.

Additional regulatory statistics gave us more insight into FedEx use of both aircraft type by sampling actual data reported by the operator.

The Memphis-Guadalajara flight (1,288 miles distance in approximately 145 minutes duration) was done by MD-10-10F carrying a 139,370 lbs payload, the MD-10-30F 172,692 lbs and the MD-11F 194,755 lbs (including 77 lbs of mail).

The Anchorage-Tokyo flight (3,433 miles distance and 412 minutes duration) was conducted by the MD-10-10F with a 138,809 lbs payload, while the MD-11F carried 194,209 lbs.

Finally for better referencing, the 4,558 miles long Paris/Memphis flight done in 533 minutes average using the MD-11F saw 194,764 lbs payload including 263 pounds of mail. We compared it to the brand new Boeing 777 Freighters acquired by FedEx which carried 235,830 lbs payload (247,000 lbs is the design maximum payload) in 525 minutes.

-FedEx has no qualms about using their largest aircraft at maximum payload on very short flight legs. This seems counter intuitive as the resulting increase in number of airframe cycles automatically shorten the airframe useful life.

-The very high load factor seen on these aircraft (0.99629 !!! is observed on a MD-11F linking Seattle to Oakland) although shocking, is symptomatic of the FedEx successful operation with large economies of scale being realized on hub-to-hub transport.

-The observed performance range of the MD-10-10F seems to indicate higher value than advertised by Boeing.

The MD-10 program is another example of 1970’s era aircraft design generating very high cargo revenues more than 40 years after first introduction. Previously we saw how Southern Air was able to build a sustainable low cost Aircraft Crew Maintenance and Insurance (ACMI) cargo airline mainly using Boeing 747-200 operating in the 100 tonnes market segment. FedEx highly integrated hub-to-hub system has seemingly been designed to uniquely leverage on the DC-10 family of aircraft specific main deck and lower deck configuration, a versatile combination of palettes, LD-3 containers and bulk cargo that maximize utilization of space as observed by the 0.99 load factor value.
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